Is Diabetic Nerve Damage Linked to Symptoms of Depression?

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Diabetic peripheral neuropathy and depressive symptoms: the association revisited, by L. Vileikyte and colleagues. Diabetes Care 28:2378–2383, 2005.

What is the problem and what is known about it so far?

Diabetic peripheral neuropathy, or nerve damage in the toes, feet, and sometimes hands, affects up to 50% of patients with diabetes. People who have diabetic nerve damage either have no feeling in their extremities, most commonly in their feet, or they feel constant pain in their toes, feet, and/or hands. The most serious complications of diabetic nerve damage, such as foot ulceration (or foot sores) and amputation, are linked with high health care costs, loss of work time, and a lowered quality of life.

Some studies have suggested that diabetic nerve damage is also linked with symptoms of depression. However, other studies have found no link between diabetic nerve damage and symptoms of depression. This may be because the different studies used different tests to diagnose nerve damage and to look at the link between diabetic nerve damage and symptoms of depression.

Why did the researchers do this particular study?

The researchers wanted to look at the link between diabetic nerve damage and symptoms of depression in patients whose nerve damage was diagnosed by well-established tests.

Who was studied?

A total of 494 patients who had diabetic nerve damage diagnosed by well-established tests (the Neuropathy Disability Score and the Vibration Perception Threshold). The average age of the patients was 62 years; 70% were men; and 72% of the patients had type 2 diabetes, while 28% had type 1 diabetes.

How was the study done?

The researchers used a well-established test to identify and measure symptoms of depression in the 494 patients who had diabetic nerve damage. The researchers also used tests and instruments to measure symptoms of diabetic nerve damage, how active the patients were, and the patients' perception of themselves and their illness and symptoms.

What did the researchers find?

The researchers found that symptoms of diabetic nerve damage were linked to symptoms of depression. In particular, symptoms of depression were found in patients who experienced unsteadiness on their feet.

To a lesser degree, symptoms of depression were also found in patients who thought the symptoms of diabetic nerve damage were unpredictable, or changed from day to day; patients who thought that there was very little that could be done to improve their symptoms of diabetic nerve damage; patients who experienced lower activity levels because of their symptoms; and patients who thought of themselves as a burden to the people they are close to.

Surprisingly, there was no link between symptoms of depression and having diabetic foot sores.

What were the limitations of the study?

Given the design of this study, there's no way to determine whether symptoms of depression are a result of having symptoms of diabetic nerve damage or, rather, whether people who already have symptoms of depression are more likely to have a negative perception of their illness, its symptoms, the treatment of diabetic nerve damage, and how it affects relationships with others.

In addition, this study did not take into account other biological factors, such as increased levels of interleukin-6. Interleukin-6 is a substance found in the body that improves the body's response to infection and disease. During times of severe illness, levels of interleukin-6 are increased, sometimes resulting in "sickness behavior," which may account for some of the link between symptoms of depression and diabetic nerve damage.

What are the implications of the study?

This study confirms that people who have diabetic nerve damage have an increased risk for symptoms of depression. Unsteadiness on one's feet may be an important symptom that links nerve damage to depression. Physicians should actively ask their patients with diabetic nerve damage about unsteadiness, especially since physical therapy and gait training may help them overcome this disability.

FOR MORE INFORMATION

Diabetic Neuropathy (Nerve Damage) and Diabetes

Additional Specific Types of Diabetic Neuropathy

Preventive foot care in diabetes. Diabetes Care 27 (Suppl. 1):S63–S64, 2004.